MUCH is written upon the subject of soil exhaustion in Africa, and it seems to be generally accepted that the soils of the tropics require careful management, including frequent periods of rest, if fertility is to be maintained. In the great clay plains of the Sudan1 in particular, it has been emphatically stated that uncontrolled continuous cultivation of land around water points and villages is responsible for the poor crops and general poverty of the villagers, and that only the provision of new villages at new water points, where cultivation can be rigidly controlled, can solve the problem. It cannot be doubted that soil erosion is responsible for reduction of yields in some cases. The question then arises, what is the reason for the very markedly poor yields of the grain and fodder crop, Sorghum vulgare, Pers., on the village cultivations, where soil erosion is not marked? The answer in the northern and central Sudan seems to be the root parasite Striga hermontheca, Benth., which is prevalent in more or less degree wherever this crop is grown, being indigenous as a parasite of the native grasses. By suitable treatment with hormone weedkillers2 it has been shown that it is possible to kill much of the Striga and bring about very considerable increases in yield on irrigated land. During the 1952 season, an experiment was carried out on a piece of village land near Gedaref, in the eastern Sudan, which has been under cultivation for longer than can be remembered by the oldest inhabitants. The result was that sorghum on the untreated plots yielded 427 lb. of heads to the acre, whereas that on plots treated against Striga yielded 1,183 lb. of heads to the acre (P better than 5 per cent). This latter would be a fairly good yield for newly opened land.